leaky sky lite ports what's the best caulk to use

[sluggo]

I have a10 meter mid cabin (2 side port widows, 2 sky lights, a step up to the helm from the rear deck I think makes it a mid cabin) anyway, the sky lights are leaking, the 'glass' is okay, but I tried to re chaulk them last yr using what the local auto glass guy recommended, but they leak. so I am asking you guys:
1) what caulk to you recommen
2) what is your step by step process??

thanks!!

[aaronbocknek]

I have a10 meter mid cabin (2 side port widows, 2 sky lights, a step up to the helm from the rear deck I think makes it a mid cabin) anyway, the sky lights are leaking, the 'glass' is okay, but I tried to re chaulk them last yr using what the local auto glass guy recommended, but they leak. so I am asking you guys:
1) what caulk to you recommen
2) what is your step by step process??

thanks!!

my slip neighbor, mike, had the same problem a few years ago and he finally solved it i believe. mike, do you want to field this one?
tri cabin aaron

[rooferdave]

being in the waterproofing business (not marine though) I have been paying attention to boat water issues. Temco makes a 1 part polyurethene product called dymonic. I have had great success with this product both on my boat and in the field. It comes in many colours and has a 20 year lifespan while remaining flexable.

http://www.tremcosealants.com/

they also have awesome tech support. However I would like to see what the more experienced here have to say

[Mike Kulp]

Hey Sluggo I can feel your pain, I had my sky lights in and out multiple times and had used 4200 & 5200 only to discover that they attack the plexiglass and make it brittle. I eventually used a boat life product that was for a silicone but the strength of 4200. I can not remember the exact name so I do not want to miss lead you by guessing. If you research the boat life products it should be easy to find. I am sure there are other products that will work also. I also noticed every time they picked my boat with the travel lift the sky lights would leak I guess from squeezing the hull. When you go to install the sky lights, clean all surfaces very good, set the sky light in dry and decide were your silicone edge will be, tape off the surface off the boat and the sky light inside and out. By some plastic squeges for body work, run a large bead in the area were the sky light sits, press in the sky light fill the void completely to the top and use the squeeges to work in the silicone, there can be no air pockets in the silicone because when it cures it makes a gas and will push through the silicone and make a leak. My friend told me this is how they install windows in air planes, since I have done it this way it has been 7 years with no leaks. Once the silicone starts tacking up pull the tape off while it is still wet and do not touch it again till it dries. If you need any more advice Email me.

[BobCT]

do you mid cabin guys have screws in the fixed portlights as well? I had two new ones made last year and replicated what was already there which has two screws in each of the 4 sides.

Anyway, I used DOW 395 adhesive along with plastic washers (as shims) along the edge so you get a nice bead that doesn't get compressed out. This stuff is designed for structural adhesion on Lexan, Plexi, etc. If I had it to do over again, I would have installed using only the adhesive but it's too late now. I don't have any leaks and they got really tested through the hurricane.

I also used the same stuff to fill the gap around the perimeter. It's ok but I still haven't found any product that doesn't attract dirt. It'll clean up with some scrubbing but won't stay white on its own. 4000 does the same thing....

Ideally, I would like to have a trim piece made out of stainless that would go around the perimeter which would solve this probem for good.

[Mike Kulp]

My sky lights have no screws just held in by the silicone.

[sluggo]

My sky lights have no screws just held in by the silicone.

thanks guys keep it coming. from what I have been told (John at marine tech) they aren't supposed to have screws. that somewhere along the lines of ownership, somebody decided that they needed screwed down (and they did with mine) I think I've used the wrong caulk and was looking for ideas. sometimes I think it is the screw hole leaking, but I ususally fill them with caulk before I screw in the screw, may want to try ot get more in the screw hole.

[sluggo]

do you mid cabin guys have screws in the fixed portlights as well? I had two new ones made last year and replicated what was already there which has two screws in each of the 4 sides.

Anyway, I used DOW 395 adhesive along with plastic washers (as shims) along the edge so you get a nice bead that doesn't get compressed out. This stuff is designed for structural adhesion on Lexan, Plexi, etc. If I had it to do over again, I would have installed using only the adhesive but it's too late now. I don't have any leaks and they got really tested through the hurricane.

I also used the same stuff to fill the gap around the perimeter. It's ok but I still haven't found any product that doesn't attract dirt. It'll clean up with some scrubbing but won't stay white on its own. 4000 does the same thing....

Ideally, I would like to have a trim piece made out of stainless that would go around the perimeter which would solve this probem for good.

Dow 395? does it have another name?? or can you tell me where you got it, I am having a hard time finding this product! thanks!

[BobCT]

Not knowing any different, I brought my old ones in (with holes) and they made them the same. After sitting for a couple of weeks screwed down, I removed all the screws and just filled the holes with the DOW 795 (I said 395 in my prior post).

If you remove the portlight and re-bed with this stuff, you can do what I did and just fill the holes completely.

If you're lucky enough not to have the holes to begin with, even better.

[sluggo]

Not knowing any different, I brought my old ones in (with holes) and they made them the same. After sitting for a couple of weeks screwed down, I removed all the screws and just filled the holes with the DOW 795 (I said 395 in my prior post).

If you remove the portlight and re-bed with this stuff, you can do what I did and just fill the holes completely.

If you're lucky enough not to have the holes to begin with, even better.

got some Dow 795, took out the hatch/light cleaned off all of the old gunk, ran a bead of the new stuff in the opening, replace the hatch/light, and ran another bead around everything, including caulling the screws. so far so good, but it isn't raining!!!
we will have some later this week so we will see, should give it plenty of time to cure.